! q; c1 Z; @9 p# @6 m( d下面是英文报道的详细油门踏板改装步骤。大家可以看看。1 b; P$ A1 V9 ~& r i z
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The CTS pedal has a friction arm that is designed to generate a certain degree of friction necessary for the proper functioning of the electronic gas pedal. In our earlier tear down and analysis, we pointed out that the CTS design is inferior to others, such as the Denso unit also used in Toyotas. The friction arm is subject to wear and contamination that increases friction to the point of creating a sticky gas pedal. - q1 o# [6 W" i$ u2 }The friction arm is a pivoted fulcrum; the end with the “friction teeth” rides in two grooved channels in the pedal assembly. Both these parts are made from plastic. The other end of the friction arm is held in place by the return spring, which exerts the pressure necessary to generate the friction. As the friction teeth wear, the gap on the other end increases in relation to the housing. Toyota’s shim is inserted in this gap in order to reduce/limit the amount of friction, and to compensate for wear.1 E9 g$ D$ Q. ^2 ]
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The gap is to be measured by a feeler gauge (photo above), which determines the thickness of shim that is then inserted in the gap. The shim then limits the travel of the fulctum on the spring end, thereby reducing the amount of friction on the teeth as they ride in the grooves.3 p/ w: G3 ]' `. U( [6 G9 [
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The next step is to open the gap by inserting a narrow-shank screwdriver, so that the correctly-sized shim can be installed. The unit has been turned upside down to facilitate that.2 V$ S, Q% E2 h
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The shim (gray steel) is now slid in, and positioned behind a lip that serves to retain it. The shim is kept in place by the pressure of the return spring on the fulcrum, but we wonder whether a strong jolt might not be able to dislodge it. If it did become dislodged, it could potentially cause serious problems. No one would ever design a unit like this with a loose metal shim that was held in place by spring pressure only.1 l$ j5 ]$ s$ g, J1 A) W$ p& m! T: y
. m, q( w! O5 l' hThe next picture shows the shim all the way in place behind the lip. It’s a good thing that lip exists, otherwise this fix would not be possible. 3 z9 A1 O9 E/ W5 m
1 W6 Z9 X% h) e5 }: Q- GThe photo above shows the inside of the unit, with the friction arm extending forward. The shim is clearly visible as the shiny gray rectangle. The pivot axles extending out on both sides of the fulcrum/friction arm are visible as two small white/gray pieces, just below and to both sides of the shim. The friction teeth are visible towards the front of the unit, riding (now higher) in their grooves. : z! k; W; Z0 V: l" e: ~
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This photo above was taken previously of the same pedal. It’s difficult to tell exactly from the slightly different angles whether the teeth are riding higher with the shim, but it does appear so. And a subjective impression was that the pedal had somewhat less friction. So the fix may well reduce the friction below a dangerous level, but for how long?3 g, }4 x$ k& o, i+ \! U
The only way we interpret the necessity of measuring the friction arm gap and choosing an appropriately sized shim is that the older units with more wear will have a smaller gap than the new(er) ones. The shim will compensate for that wear, but in a static, not dynamic way. As soon as the continued wear on the friction arm changes its size or other friction characteristics, the pedal is potentially back to the same sticky situation as before. 3 A' o6 B9 ~. A* \' R, X' ` ]The shim’s effect on reducing the amount of friction will presumably slow down the wear process, but intrinsically, this is not a permanent fix to a very critical part, from a safety point of view. This is why the CTS-type pedal design is flawed, because it is subject to changes in the amount of friction it generates due to wear and other factors. 8 i6 y% m/ W: QThe only other explanation for the varying gap size and different shims is that the manufacturing tolerances are so great, that this is necessary to compensate for them. That’s that hard to imagine, for such a critical part. But if so, it raises other serious questions about this unit. Either way, it reinforces our position that Toyota needs to replace all the CTS pedals with Denso pedals or another proven pedal design, as soon as they are available. The shim fix is a Band Aid, and does not inspire the confidence that Toyota urgently needs to instill in its customers and the market place at this critical time.) G9 O+ V4 L/ R- E+ e7 q Update: Given that Toyota has acknowledged that these pedal assemblies cost them $15, it would obviously be cheaper (and more reliable) to swap out the CTS units with the Denso unit rather than this fussier and riskier fix. The problem is time; it could take many months if not a year or more to change tooling and produce 2.3 million units. Meanwhile, making these shims was obviously something that a stamping manufacturer could do in days. , f/ s: P: x# c/ v' x8 {再次用老农民都看得懂的语言解释一下刹车系统与真空的关系: : f0 Y3 G9 y2 X' T* N6 \$ H/ P" `3 d1 V; K& L
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刹车是靠真空助力的,这句明白不?明白了,咱来下句: * r/ F5 h/ `, |, {) m* p4 g9 d# w" ?% ~0 ~8 G6 S
真空管里的真空取决于油门。当油门最小时,真空最大;油门最大时,真空为零。刹车需要的真空助力是-17,油门最大时,就达不到了,理论上虽然不等于零,但对刹车来说,就没用了。这句可能不容易明白,但这是事实。1 n1 n( S" y/ `& b; Q8 m
解释一下原理: 9 N# u4 u+ W' Z, i/ H/ z2 z) ^% j; M2 p
你把一个吸管放入你的嘴里,另一头用手指堵上,然后,你用嘴吸吸管。你的手指头相当于油门。你本身是发动机。 # ~$ U; V( h) h& m( Z9 x发动机不转,就等于你的嘴巴不吸吸管。当你把手指头松开一点点,此时“发动机”就是你的嘴巴开始吸,4 F3 m; C1 Q' i! x* v
手指头不松开的时候你的嘴巴也不吸。: |8 q0 @* j. Z
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当你的手指头松开最小的时候,比如挡住吸管99%,你用力吸,此时吸管里的真空最大。等你把手指头全部放开,0 j/ [; y! X+ t6 s# M, m$ O
吸管里就没有了真空! , L- t0 {0 G8 t6 x: n $ s" J4 N+ e6 g& r. C如果这个吸管也通往刹车系统,没有了真空,刹车就没有了助力。(这个吸管的比喻是我在车坛的朋友TBx形象地比喻,! [- w8 z% c( b s9 c9 j( e% P
比我用发动机的构造作解释对于外行人搞明白容易多了。)$ `# D+ g8 {1 G: I
0 ~3 C) H5 Y0 ]4 I A. l& T. G能听明白不?如果还是有人听不明白,那就自己用吸管示范一下,如果吸管是软的,你用力吸,手指放开很少堵的比较严 A% U: ~" R2 X' C' f的时候,吸管会瘪下去的,因为真空的原因。嘴巴就等于发动机,你的手指就等于油门。作者: 德国的牛 时间: 2010-4-9 14:38